Photonic waveguide investigation for development of fusion applications

In this work we present a literature review of novel photonic waveguides, modeling of such waveguides in the microwave regime, and various recommendations for development of waveguides for future fusion applications. Extremely low attenuation microwave transmission lines are necessary for various millimeter wave and terahertz applications, such as RF heating and current drive in magnetic fusion devices, as well as microwave-based plasma diagnostics. Such low attenuation is usually achieved by designing a large cross section relative to the wavelength of the transmitted wave. This overmoded structure allows more than one propagation mode to be transmitted. The hybrid electric HE11 mode is favorable because it is low loss and relatively robust to mode conversion. As corrugated waveguides are limited by manufacturing constraints, alternative waveguide geometries are necessary to transmit higher frequency waves. One such approach is a dielectric coated smooth-wall overmoded waveguide [see Thackston et al. J Infrared Milli Terahz Waves 44, 473–488].